To find : weight of steel per metre.
Since the formula to be derived is d^2/162, assumed cross section is circular and the material is cylinder.
Weight density of steel = 7850 kg/m^3.
| Rod Number | Rod Size (in) |
Rod Weight (lb per linear foot) |
|---|---|---|
| 2 | 0.250 = 1/4″ | 0.17 |
| 3 | 0.375 = 3/8″ | 0.38 |
| 4 | 0.500 = 1/2″ | 0.67 |
| 5 | 0.625 = 5/8″ | 1.04 |
| 6 | 0.750 = 3/4″ | 1.50 |
| 7 | 0.875 = 7/8″ | 2.04 |
| 8 | 1.000 = 1″ | 2.67 |
| 9 | 1.128 = 1 1/8″ | 3.40 |
| 10 | 1.270 = 1 1/4″ | 4.30 |
| 11 | 1.410 = 1 3/8″ | 5.31 |
| 14 | 1.693 = 1 3/4″ | 7.65 |
| 18 | 2.257 = 2 1/4″ | 13.60 |
Formula:
Weight density = weight/volume.
Weight = weight density x volume.
Volume of cylinder= πh d^2 /4
h is the height of cylinder bar. = 1m
d is diameter in mm
Volume = 3.14/4 x d^2 x 10^-6.(converted mm to m two times for d)
Volume of cylindrical bar = (7.85 x 10^-7) d^2 cum
Weight of cylindrical bar
= 7850 x 7.85 x 10^-7 x d^2.
= 0.00616 x d^2
= d^2 /(0.00616^-1)
= d^2/162.3
~ d^2/162
Since d’s unit is converted into the formula from mm to m, you can directly use the dia number to find out the weight per metre. For example:
25 mm dia bar:
625/162 = 3.85 kg
